In a wand type bar code scanner, it would be desirable if the entire scanner system were operable under a wide variety of conditions of label reflectivity and background illumination while operating with a single low supply voltage, e.g. five volts. It is found however, that a conventional digitizer circuit for the bar code signals lacks the dynamic range to handle the requisite reflected light intensity variations, with such a low supply voltage.
In the practical manufacture of optical scanner tips, it is found that there is a substantial variation in the optical parameter which is known as optical offset. Optical offset results from varying degrees of light leakage between a light emitting section and a photodetector section, and is entirely distinct from the electrical leakage current or "dark current" which is present when the light source is de-energized.